Solid state lighting (SSL) such as LED lighting is becoming increasingly popular because of the energy efficient nature of such lighting as well as the lifetime of such lighting. Consequently, traditional light sources such as incandescent lamps and halogen lamps are being replaced with LED lighting.
In most applications, a LED lamp comprises a plurality of SSL elements, i.e. individual LEDs to produce the desired luminous flux. Such LEDs may be arranged on a carrier such as a printed circuit board (PCB) in a regular or irregular pattern, e.g. a grid of LEDs. In order to achieve the desired luminous distribution from such an arrangement, the carrier may form part of a LED assembly in which one or more optical modules are positioned over the carrier. An example of such an assembly is disclosed in US 2014/0192529 A1. Such LED assemblies for example are commonly used in outdoor luminaires. This is explained in more detail with the aid of FIG. 1, which schematically depicts such a LED assembly 1 in an exploded perspective view, and FIG. 2, which schematically depicts a cross-sectional view of part of such an assembly.
The prior art LED assembly 1 comprises a carrier 10, e.g. a PCB, onto which a plurality of LEDs 20 are mounted in a regular pattern. Here, a plurality of optical modules 30 are mounted on the carrier 10 such that each LED 20 is aligned with an optical element 31, e.g. a collimator, lens or the like, of the optical module 30 to shape the optical output of the LED 20, e.g. to convert the Lambertian luminous distribution of the LED 20 into a (more) collimated luminous output. A number of optical modules 30 may be combined to form an optical plate covering the carrier 20 in case of a large area carrier 20, which may be desirable to avoid the manufacture of an overly large single optical module 30 acting as an optical plate, e.g. for cost reasons.
As can be seen in FIG. 2, and as can be readily understood by the skilled person, in order for the optical element 31 to perform its desired optical function, the optical element 31 needs to be positioned at the correct distance H2 from the LED 20, e.g. the focal distance of the optical element 31. To this end, the optical module 30 may comprise a plurality of mounting posts 33 that define a height H3 at which the optical module is positioned over the carrier 10, thereby optically aligning each optical element 31 with a LED 20 on the carrier 10.
However, different types of LED 20 may have different heights H1, for example because the substrate 21 of the LED 20 and/or one or more light conversion layers 23, e.g. phosphor layers, may have different thicknesses. Consequently, whenever a type of LED 20 is changed on a carrier 10, e.g. to alter the luminous flux of the LED assembly 1, to replace a LED 20 with a cheaper alternative, and so on, this typically causes a change in the height H1. As will be understood from the above, this therefore also requires a change of optical module 30 in order to ensure that the optical module has the correct mounting height H3 relative to the carrier 10 such that each optical element 31 is positioned at the correct height H2 over the LED 20, as use of an optical module 30 at an incorrect height H3 such that the optical elements 31 are positioned over the LEDs 20 at an incorrect height H2 may cause the LED assembly 1 to produce a suboptimal luminous output, i.e. a luminous output having a suboptimal luminous distribution, e.g. a blurred luminous output, a luminous output with an incorrect degree of collimation, and so on.
Having to replace the one or more optical modules 30 each time the LEDs 20 on the carrier 10 are being replaced with an alternative is rather costly. What is more, before the optical modules 30 can be manufactured, a decision has to be made about which LED 20 is going to be used on the carrier 10 in order to ensure that the mounting posts 33 of the optical modules 30 are set to the appropriate height H3. Consequently, it is not possible to make a last-minute decision about which LEDs 20 to use on the carrier 10, which may be desirable for instance for economic reasons, i.e. such that the manufacturer of the LED assembly 1 can choose the cheapest suitable LED 20 available on the market. This is an important consideration in the field of solid state lighting, where profit margins are notoriously suppressed due to the high levels of competition in this field.
JP2009230984 discloses a lens mounting substrate to be mounted with a lens, said lens having a fixed leg body for changing the mounting height of the lens.